Proteases, monoclonal antibodies, and glycosylation inhibitors have provided probes of the organization and activities of adhesive glycoproteins. Protease-resistant and susceptible regions were identified; fibronectin molecules from chicken and human sources were found to retain nearly-identical functional domains for binding to collagen, fibrin, heparin, and other molecules, yet to display variable interdomain regions. These results suggest the evolutionary conservation of functional domains, but not of interconnecting, flexible interdomain polypeptide regions. Retinoic acid increases cell adhesion and may inhibit tumorigenesis. Its molecular mechanism of action was examined in chondrocytes, where it was found to alter glycosylation of fibronectin. Chondrocyte fibronectin was characterized by high-mannose or hybrid N-linked oligosaccharide chains. Treatment with retinoic acid caused a reversion of the structure of these chains to the complex form characteristic of fibroblast fibronectin. These results appear to be the first demonstration of retinoic acid regulation of the glycosylation of a specific glycoprotein. Additional experiments in progress are using the glycosylation inhibitor tunicamycin to help identify critical functional sites on fibronectin for binding to collagen, as well as proteases to generate mitogenic activity from fibronectin. A monoclonal antibody library for membrane proteins identified in immunoblots has been established, and is being applied to identify and characterize new glycoconjugates. Our objectives will be to continue to use proteases and glycoconjugate probes to identify a small, functionally-essential site in fibronectin for its binding to collagen and to test the role of carbohydrates in protection of function, to determine the origin of the mitogenic activity of proteolytically-cleaved fibronectin, and to use the monoclonal antibody library to characterize novel glyconjugate functions, especially in cell adhesion.